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Synthesis and Analysis of Biodiesel Unit

Synthesis and Analysis of Biodiesel Unit
Contributors
Beyond Benign, Inc.
Retired K-12 Educator | Beyond Benign, Inc.
Science Done Sustainably
Beyond Benign, Inc.
Learning Objets
Summary
Fossil fuels (natural gas, coal, oil) are non-sustainable and non-renewable resources that our current society has become heavily dependent on. Petroleum (literally rock oil) is the source of gasoline and diesel gas, two common fuels that keep our automobiles running. Prices of these petroleum based fuel are rising due to their high demand and scarcity. In addition, the burning of these fuels increase society’s ecological footprint and add to the greenhouse effect, which underlies global warming. This lesson demonstrates to students the sustainability of a renewable resource, biodiesel.

Biodiesel is a fuel made from vegetable oil through a reaction called transesterification. Transesterification is a reaction between an ester and an alcohol in which the -O-R group of the ester and the -O-R' group of the alcohol trade places.

The main component of vegetable oil is a molecule called triglyceride (also known as triacylglycerol). Triglyceride is composed of a glycerol group linked by an ester bond to 3 fatty acid molecules. Figures 2, 3 and 4 show the chemical structures of triglyceride, glycerol and fatty acids.

The ester group in triglyceride will exchange places with the alcohol group in methanol or ethanol* to form biodiesel. Biodiesel is a methyl or ethyl ester (depending on whether methanol or ethanol is used) of a long chain fatty acid hydrolyzed from triglyceride.

The chemical composition of diesel is about 75% saturated hydrocarbons (primarily paraffins including n, iso, and cycloparaffins), and 25% aromatic hydrocarbons (including naphthalenes and alkylbenzenes). The average chemical formula for common diesel fuel is C12H23, ranging from approx. C10H20 to C15H28. The heat of combustion of diesel = 10,700 cal/g.

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Moderation state
Published
Object Type
Laboratory experiment
Audience
High School (Secondary School)
Published on
Green Chemistry Principles
Designing Safer Chemicals
Use of Renewable Feedstocks
Catalysis
Real-Time Pollution Prevention
Safer Chemistry for Accident Prevention
NGSS Standards, if applicable
• HS-PS1-2. Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns in chemical properties.
• HS-PS1-4. Develop a model to illustrate that the release or absorption of energy from a chemical reaction system depends upon the changes in total bond energy.
• HS-PS1-5. Apply scientific principles and evidence to explain how the rate of a physical or chemical change is affected when conditions are varied.
• HS-PS1-7. Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.
Learning Goals/Student Objectives
Learning Goal:
The goal of this unit is for the students to understand that our current practices of burning gasoline and diesel gas for automotive transportation is not sustainable and has a big ecological footprint. Students will learn about a renewable resource that may be able to replace gasoline and diesel fuel one day. By synthesizing biodiesel, students will learn how it is made and where it comes from. By analyzing biodiesel, students will be able to evaluate the likelihood biodiesel is to eventually replace gasoline and diesel gas as our primary transportation fuels.

Student Objectives: Students will …
• Determine the properties of various cooking oils
• Synthesize biodiesel
• Determine the properties of their biodiesel
• Analyze biodiesel’s heat of combustion
• Assess whether biodiesel can be used in transportation vehicles or not
Common pedagogies covered
Hands-on learning
Time required (if applicable)
Six 30-45 minute class periods

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Safety Precautions, Hazards, and Risk Assessment
Safety Information: Although the acetic acid is a weak acid, do not allow direct contact with skin nor ingest the 0.1 M acetic acid.
Digital Object Identifier (DOI)
https://doi.org/10.59877/KYLN6921

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